Conventionally, a power module using a switching element for use in various fields often adopts a resin sealed structure for the purpose of an increase in reliability of an electronic component or an increase in manufacturability of a module. The amount of heat generation of a power module has a tendency to increase according to multi-functionalization, increased power output, and high density packaging of a power module. The power module of such a resin sealed structure covers a switching element-equipped conductor portion with resin and exposes a heat dissipation layer of the back surface in order to increase the heat dissipation property. Furthermore, surface contact with an external module attachment portion is provided through grease, insulation sheet or the like, so that a heat dissipation route for dissipating heat generated by the internal switching element to the outside is secured. When such a structure in which the reliability is maintained and the heat dissipation route can be secured is adopted, the heat generated by the switching element is thermally diffused by the heat dissipation layer and the heat can be effectively dissipated to the module attachment portion over a large area.
When the heat dissipation layer of the back surface is not exposed, but is overmolded with resin and resin having excellent heat conduction property is used, the usage of grease, insulation sheet, or the like, which is an insulation member, can be reduced. In addition, for example, as disclosed in PTL 1, when the heat is dissipated not only from one surface of the power module, but also from both surfaces to the outside, the heat dissipation performance can be increased and the size can be reduced.